Hydrogen-rich gas generator

ABSTRACT

A process and apparatus is described for producing a hydrogen rich gas by introducing a liquid hydrocarbon fuel in the form of a spray into a partial oxidation region and mixing with a mixture of steam and air that is preheated by indirect heat exchange with the formed hydrogen rich gas, igniting the hydrocarbon fuel spray mixed with the preheated mixture of steam and air within the partial oxidation region to form a hydrogen rich gas. The apparatus for performing the process is in the form of a bell-shaped chamber which consists of an open cylinder wherein a partial oxidation reaction takes place. An air pasageway and a pipe for injecting water into the passageway are provided for forming a steam-air mixture. The air is preheated indirectly by the heat generated as a result of igniting a hydrocarbon fuel spray and thus the water is converted into steam when injected into the preheated air. The air-steam mixture is then conducted through a region of the hydrogen generator where a plurality of pipes are spaced and arranged to provide a heat exchange baffle. These pipes conduct the hydrogen rich gas after it has been generated in the open cylinder.

ORIGIN OF THE INVENTION

The invention described herein was made in the performance of work undera NASA contract and is subject to the provisions of Section 305 of theNational Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat.435; 42 USC 2457).

This is a division of application Ser. No. 428,444, filed Dec. 26, 1973,now U.S. Pat. No. 3,920,416.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to generators of hydrogen rich gas and moreparticularly to improvements therein.

2. Description of the Prior Art

In an application for patent by Houseman, et al, Ser. No. 390,049, filedAug. 20, 1973, and assigned to a common assignee, there is described andclaimed a hydrogen rich gas generator comprising a chamber wherein airand hydrocarbon fuel are injected into one end of the chamber whereinthey are mixed and then ignited to provide very hot combustion gases, bypartial oxidation. These gases move away from the ignition region toanother region in the chamber where water is injected to be turned intosteam by the hot combustion gases. Either simultaneously with theinjection of water or subsequently thereto, more hydrocarbon fuel isinjected. The steam which is formed mixes with the hot gases present anda steam reforming reaction with the hydrocarbon fuel takes place toproduce a hydrogen rich gas.

While the described arrangement does provide hydrogen rich gases, italso has a tendency to form carbon. Since one of the purposes of thehydrogen generator is to provide hydrogen gas to be used in an internalcombustion engine, the presence of the carbon which is generated isundesirable since it tends to clog up the induction system of theinternal combustion engine.

It was also found that the yield of the hydrogen rich gas that wasobtained was not as large as was to be expected because of heat lossesfrom the generator due to the distances between injection points, beforethe steam reforming reaction occurs.

OBJECTS AND SUMMARY OF THE INVENTION

An object of this invention is the provision of a novel method and meansfor minimizing the carbon output of a hydrogen rich generator of thetype described.

Still another object of this invention is the provision of a novelmethod and means for increasing the hydrogen content output of ahydrogen rich gas generator of the type described.

The foregoing and other objects of the invention may be achieved bypreheating the input air, then injecting atomized water into thepreheated air stream and after some more preheating, the resultingsteam-air mixture is introduced into the flame zone. An alternate methodis to atomize the water and introduce it directly into the flame zone.

Yet another method is to introduce the water directly into the primaryflame zone as an emulsion of water and hydrocarbon fuel.

As a result of introducing all ingredients required into the flame zoneand no place else, carbon formation is eliminated as well as thenecessity for using a secondary hydrocarbon injection since all thehydrocarbon required is being entered into the generator through theprimary fuel nozzle.

The novel features of the invention are set forth with particularity inthe appended claims. The invention will best be understood from thefollowing description when read in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an embodiment of the invention, in section, wherein steamis generated external to the generator.

FIG. 2 is a cross-sectional view of the embodiment of the inventionillustrating how steam can be generated within the generator.

FIG. 3 is a view in section illustrating another embodiment of theinvention.

FIG. 4 is a view in section illustrating still another embodiment of theinvention.

FIG. 5 is a view in section illustrating another arrangement for theinvention.

FIG. 6 is a schematic arrangement illustrating the start up and turn offsequences of the generator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, there may be seen a view in cross-section of animproved hydrogen generator in accordance with this invention. Thiscomprises a bell-shaped chamber 10 having an outer wall 12, and an innerwall 14, spaced therefrom, with thermal insulation 16 therebetween.Spaced from the inner wall 14, is yet another wall 18, which forms anair passage with the inner wall 14.

Air from a pump or compressor, not shown, is introduced into the airpassage by means of an induction pipe 20. The inner wall 18 surroundsthe hot region of the hydrogen generator and therefore, the air flowingthrough the passageway is preheated. The preheated air flows into a pipe22, which joins with a chamber 24, into which a water spray isintroduced by means of a spray nozzle 26, which is connected to a waterpump, not shown.

The water spray is converted into steam in the chamber 24. Chamber 24conducts the steam and air mixture, through a pipe 27, back into aregion of the hydrogen generator where a plurality of pipes 28, arespaced and arranged to provide a heat exchange baffle. These pipes 28conduct the hydrogen rich gas, after it has been generated, to an outputchamber 46 from which the gas is sent to user equipment through a pipe30, to which the user equipment, such as an internal combustion engineis connected.

The steam and air mixture circulates through the pipe baffle, beingstill further heated thereby, and serves to cool down the hydrogen richgas which passes through the pipes. The air-steam mixture is thenconducted from the pipe baffle arrangement by means of passageways 32,34, through a set of vortex baffles 36, into a region of the reactor inwhich partial oxidation of the hydrocarbon fuel, which is alsointroduced into this region, takes place. Simultaneously with thepartial oxidation reaction, steam reforming takes place.

It should be noted that what is introduced into the partial oxidationregion through the vortex baffles is a mixture of air and steam whichare formed into a vortex by the pressence of these baffles 36.

A tube 38, has one end connected to a hydrocarbon fuel pump, not shown,and the other end introduces liquid hydrocarbon fuel in the form of aspray into the partial oxidation region. Because of the vortex createdby the air-vortex baffles, an excellent mixing of the steam-air mixtureand fuel takes place. The mixture is ignited by a hot wire, or sparkigniter 40. The relative quantities of air, fuel and water are such thatpartial oxidation and steam reforming of the hydrocarbon takes placesimultaneously while carbon formation is avoided. By way ofillustration, and not as a limitation on the invention, hydrocarbon fuelwas supplied at a rate on the order of 2 gallons/hour. Air was suppliedunder a pressure of between 2 to 5 psi. A water to fuel ratio of between0.5 and 1.2 was employed.

The presence of steam aids considerably in suppressing carbon formation.Combustion takes place under fuel rich conditions, with steam dilution,with accompanying low flame temperature, so that very little nitricoxide is produced. In view of the manner of introduction of the fuel andair-steam mixture, a vortex-type flame is provided with a high degree ofturbulance, which aids in thoroughly mixing the air, the steam and thefuel and which promotes flame stabilization.

The partial oxidation reaction is virtually completed within the space42, established by the open cylinder 44, which is supported adjacent theregion where the fuel and steam are introduced. However, steamreforming, takes place within the partial oxidation region 42, and alsoin the annular space defined between the walls 18 and the cylindricalwalls 44. The annular space between the walls 18 and the cylinder walls44, also serves to thermally insulate the space 42 confined within thecylinder 44 so that a high reaction temperature within the cylinder ismaintained.

The walls 18 are heated up because of the reaction which takes placeadjacent thereto and thus, the air passing on the opposite sides ofthese walls is preheated. The hot product gases resulting from thereaction flows through the tubes 28 where they are partially cooled,since the tubes constitute a heat exchanger whereby the incomingair-steam mixture can take on the heat of the hot product gas. The tubesterminate in an output annular space 46 which is in turn connected tothe discharge pipe 30.

Product gas will still be superheated with respect to water upon leavingthe reactor. If it is desired, the product gas may be further cooleddown to condense out the water which can be recirculated back to thewater feed tank.

In order to start up the hydrogen generator, a small diameter tube 48has one end connected to the hydrocarbon fuel pump and the other endterminates in a nozzle which is adjacent to the hot wire 40, which alsohas a small wire mesh wick surrounding it (not shown). A small amount offuel is deposited on this wire mesh wick when it is desired to start thehydrogen generator. This is then ignited by the hot wire. A temperaturesensor 50, which may be any of the well known temperature sensingdevices, such as a thermistor, or a bimetallic device, indicates when ahigh enough temperature is reached. The signal generated as a result isused to enable a supply of hydrocarbon fuel from the main supply, whichflows through pipe 38. Hydrocarbon fuel sprayed from pipe 38 is ignitedby the pilot flame at the wick surrounding the hot wire 40.

Another temperature sensor, 52, which is located in the walls at theopposite end of the container, senses when the main flame, due to theburning of the hydrocarbon supplied through the nozzle of pipe 38, hasheated up the combustion chamber walls to a sufficient degree so thatthe air temperature at the sensor 52 reaches a predetermined value. Atthis predetermined value, the sensor output signal is utilized to enablethe water nozzle 26, to supply water to bring about steam formation.

The turn on sequence described, enables rapid heat-up of the equipmentand enables attaining an air preheat temperature that is high enough toprevent liquid water accumulation in the heat exchanger during start-up.In addition, the reactor wall surface 44 is thoroughly heated up,thereby avoiding soot formation. When it is desired to shut down, theflow of hydrocarbon fuel through the pipe 38 is reduced for a fewseconds to enable a hot stream of steam containing gas to continue toflow through the whole reactor to promote gasification of any tars orsoot that may be deposited. Then, the water pump is turned off to enableair-rich hot combustion gases to sweep through the whole unit for a fewseconds to insure combustion of any deposits of tar or soot with theavailable excess oxygen. Thereafter, the fuel pump and the aircompressor are turned off. A control arrangement for sequencing turn onand turn off which may be used with this invention is shown in FIG. 6herein. By injecting all the ingredients required for making hydrogenrich gas into a single region, instead of at spaced locations along thechambers, as was done heretofore, heat losses are avoided, hydrogen richgas yield is increased and unwanted carbon is minimized.

FIG. 2 is a cross-sectional view of an arrangement of the inventionwherein the steam generation process takes place within the generator.Similar functioning parts to those shown in FIG. 1 bear the samereference numerals. Here, a pair of nozzles, respectively 60, 62,introduce a water spray, from the water pump, into the passageway whichis established between the wall 18 and the wall 14 at a locationsufficiently downstream from the location at which air is introduced toenable the air to heat up. The heated air converts the spray dropletsinto steam, and the steam is conducted through the baffle established bythe pipes 28, whereby the steam-air mixture is further heated by the hotproduct gases which pass through these pipes to the annular space 46.

The operation of the hydrogen rich gas generator is the same as has beendescribed for FIG. 1, except that, steam is now generated within thegenerator, whereas in FIG. 1 it was generated external to the generator.This is a preferred arrangement.

FIG. 3 is a sectional view of the hydrogen generator, only showing somuch of the generator as differs from the arrangement previouslydescribed in FIGS. 1 and 2. In this embodiment of the invention, anemulsion of hydrocarbon and water is made by an emulsifying agent withwater and hydrocarbon fuel. Thus, a source of the emulsion ofhydrocarbon and water 62 is provided. This is supplied through the pipe38 in place of the hydrocarbon fuel. Air is preheated in the passagewayformed in the chamber walls and is passed through the baffle region andthen through passageways 32, 34, into the combustion region. The waterin the emulsion is turned into steam by the hot gases created by theignition of the hydrocarbon fuel in the region adjacent the vortexbaffles 36. The steam reformation of the unburned hydrocarbon fuel thentakes place in the manner previously described.

By way of example, and not by way of limitation, a suitable emulsifyingagent is polyethylene (4) Laurel Ester, made by Atlas-ICI anddistributed by McKesson Chemical Company of Los Angeles. This is mixedin the proportion of 1/2 to 1% by weight of water and after thoroughlymixing is mixed with an equal volume of fuel.

FIG. 4 is a view of a section of the hydrogen generator which showsstill another arrangement. Here, a pneumatic atomizer 70 is used to mixthe water and the fuel and inject it as spray droplets into theoxidation region. A suitable arrangement for performing the atomizationis to mix the fuel and water, using a T-shaped arrangement of pipeswhich water under pressure enters one branch and the fuel under pressureenters the opposing branch to mix with water at the junction of thepipes. The mixture is then fed into the usual pneumatic atomizer.Preheated air is injected through the vortex deflectors 36 into thecombustion region. The fuel is ignited by the hot wire 40, and theatomized water droplets injected therewith are immediately convertedinto steam by the hot gases which are created. The steam reformationthen takes place in the manner described previously.

The pneumatic atomizer 70, is supplied by air under pressure from asource, not shown. This air under pressure is supplied to the atomizerfrom the source by means of a tube 72. A second tube 74, is used toconduct water from the water pump to the pneumatic atomizer. A thirdtube 76, is used to conduct hydrocarbon fuel from the hydrocarbon fuelpump to the atomizer 70.

FIG. 5 is a cross-sectional view of an embodiment of the invention usinga somewhat different physical arrangement than that shown in thepreceding drawings. However, the principles of operation are identical.Here, a somewhat cylindrical shaped gas generator is employed. The gasgenerator has two spaced walls, respectively 80, 82, between whichthermal insulation is placed. A third inner wall 84, is spaced from thewall 82, to establish a passageway. Air from a compressor is introducedinto an intake pipe flange 86. It flows over the baffle created by theplurality of spaced tubes 88. The air that passes through the baffle isheated and is then led into the passageway between walls 84 and 86.Water spray is introduced into the passageway using spray nozzles 90,92, which is supplied with water by a water pump (not shown). The hotair which has passed through the baffle, causes the water drops tobecome steam. The steam and hot air mixture are directed by the spacebetween the walls 82 and 84 into the main chamber 96 of the generatorthrough the vortex baffles 98.

Fuel from the hydrocarbon fuel pump is introduced into the vortex regionof the generator by means of a pipe 100, which has a spray nozzle tippositioned adjacent the vortex baffles 98. The procedures for startingup the hydrogen rich gas generator and for turning it off are the sameas were described in connection with FIG. 1.

FIG. 5 should be considered as exemplary of the type of a cylindricallyshaped gas generator in which the baffle is placed at the end oppositeto the combustion region. The cylindrical walls within the generatordefining the combustion region are omitted. Steam is internallygenerated in the manner shown in FIG. 2. An emulsion of hydrocarbon andwater may be injected as shown in FIG. 3, if desired, or water and fuelmay be simultaneously injected as shown in FIG. 4, through the intakeflange 102 which includes the ignitor and the pipe leading from thehydrocarbon fuel pump.

FIG. 6 is a schematic drawing of a control arrangement for the hydrogengenerator shown in the drawings. Upon turning a start-up key 110, whichcan be the ignition key for a vehicle, a double pole double throw switch114, (shown in the open position), is operated. This energizes astart-up relay 112, and charges a capacitor 116 from a power source 118.The energized start-up relay enables current to flow to activate the hotwire igniter 40, and also enables the start-up of a fuel pump 120, whichdraws fuel from a tank 122. Also, enabled to be started at this time isan air compressor 124. The start-up relay 112 also enables a relay 126to be operated. This relay energizes an ignition fuel valve 128 for ashort time whereby a small quantity of hydrocarbon fuel is applied tothe wick surrounding the hot wire igniter 40.

The temperature sensor 50 provides an output signal when it senses thata flame is present, which output signal is amplified by an amplifier130. The output of amplifier 130 energizes a relay 132, which enablesthe main hydrocarbon fuel solenoid valve 134 to be opened to supply fuelat a low rate. This main fuel spray is ignited by the pilot flame of thewick surrounding the hot wire 40.

Thereafter, when temperature sensor 52 senses that the main flame hasheated up the chamber walls to a sufficient degree, its output isapplied to an amplifier 136, whose output enables a water pump 138 to beturned on. This brings about steam formation. Another amplifier 140,also amplifies the output of the temperature sensor 52 and turns a relay142 on. Relay 142 after a short delay enables main valve 134 to beturned to its full on position which supplies hydrocarbon fuel to thereformer at a high rate.

When it is desired to shut down, the start-up sequence is essentiallyrepeated in reverse. When the ignition key 110 is turned off, the dobulepole double throw switch 114 is operated to the open position shown.Capacitor 114 enables a turn off relay 144 to be operated over as longan interval as is required for turn off. This relay enables a pulsegenerator 146 to start generating pulses. These pulses are applied to acounter 148, which in response, commences to count up. On the occurrenceof the first count, relay 142 is enabled to be de-energized and the mainvalve 134 returns to its low fuel supply rate position. A hot stream ofgas will still flow through the whole reactor to promote gassificationof any tars or soot that may be deposited.

On the second count, the water pump 138 is turned off. On the thirdcount, the relay 132 is deactivated whereupon the main fuel valve 134 iscompletely turned off.

Upon the fourth count, the fuel pump 120 is turned off, as well as theair compressor 124. Relay 144 is also turned off resulting in the pulsegenerator 146 being turned off. It should be noted that upon a newactuation of the ignition start key, the counter 148 is reset.

The circuit arrangement shown in FIG. 6 can be used without anymodifications to control start-up and turn off for the generators shownin FIGS. 1, 2, 4, and 5. For the arrangement shown in FIG. 3, the fueltank 122 will actually be a reservoir of an emulsion of hydrocarbon andwater and water pump 138 and amplifier 136 may be dispensed with.

There has accordingly been described and shown herein a novel method andmeans for generating a hydrogen rich gas using the steam reformingprocess.

This method avoids the formation of carbon by providing for a high steamconcentration in the primary flame zone. The effect of the injection ofsteam or water into the primary flame zone also lowers the primary flametemperature which prevents the pyrolysis of fuel leading to sootformation.

With this arrangement of the invention, by passing both the steam andthe hydrocarbon through the primary flame zone, the reactants passthrough the highest temperature zone which leads to a high reaction ratefor steam reforming. As a result, there is a drastic reduction in sootformation as well as an increase in hydrogen yield. Finally, thestructure of the reactor is considerably simplified.

I claim:
 1. A method of generating a hydrogen rich gas in a hydrogengenerator having a partial oxidation region comprisingintroducing aliquid hydrocarbon fuel in the form of a spray into said partialoxidation region, preheating air with the heat generated as a result ofigniting the hydrocarbon fuel spray, injecting water into said preheatedair to form a mixture of steam and air, further heating indirectly saidmixture of steam and air, mixing said further heated steam and air withsaid hydrocarbon fuel spray within said partial oxidation region,igniting said hydrocarbon fuel spray mixed with said steam and airwithin said partial oxidation region to form a hydrogen rich gas, andremoving all of said hydrogen rich gas from said partial oxidationregion.